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XTR110: Trying to get the "Basic Circuit Connection" to work...

Part Number: XTR110

I've wired up the Basic Circuit Connection in Figure 1 (page 6) of the XTR110 data sheet. 

Supply voltage is +24 volts (between pins 16 and 2). Also ran the circuit with 12v, as 24v pumps too much wattage through my load resistor (1K at this time).

Input voltage is created using a pot across Vcc/Gnd (and I'm careful not to exceed 10v to the input).

Output goes to the gate of an FQ27P06 (enhancement mode) MOSFET; I've also used an IRF9560 here. Source is connected to Vcc (24v or 12v). Drain is connected through a 1K resistor to ground.

Applying power, I get the full 24v/12v dropped across the 1K resistor. Pot position (voltage input to XTR110 can range from 0-10v, nothing changes. Measuring the output on pin 14 I always see 1.35v (regardless of supply voltage).

Pins 1 and 13 are at Vcc (or a tiny bit below).

Zero adjust, span adjust, and 4mA span are floating, 16mA span is tied to ground. Vref adj is floating.

Changing the pot value does not affect the voltage drop across the load resistor.

Any idea what I'm doing wrong?  (BTW, I've tried two separate ICs, both produce the same result).

  • Hi Randall,

    Thanks for your post. Do you have this schematic drawn out? Can you take a picture of this and share it with me? It will be easier to follow. With a 0-10V input, what is your expected output? The table at the bottom of Figure 1 will outline different options. I want to make sure everything is connected correctly (a schematic would help here).

    In the case of the 12V supply, the voltage supply range for XTR110 is 13.5V to 40V. 

    I couldn't find the datasheet for IRF9560, we need to make sure that the gate-source voltage > Vcc. 

    How are you measuring the output? DMM across RL?


  • The schematic is exactly that of the XTR110 data sheet. Figure 1, page 6 ("Basic Circuit Connection").

    I got exactly the same results using 12v or 24v for Vcc. The difference was that I had to use two 2k (1/4W) resistors in parallel (1k 1/4W was too small and I didn't have any 1/2W resistors; the 1K would get rather warm).

    Yes, I put a DMM across RL. In never varied. Always pegged at Vcc, regardless of the Vin value (0-10v).


    Drain-Source Voltage VDS - 100 V

    Gate-Source Voltage VGS ± 20V


    VDSS Drain-Source Voltage -60 V

    VGSS Gate-Source Voltage  ±25 V

    I'll see if I can dig up a 15v power supply, though 24V seems like the idea conformance voltage.

  • Hi Randall,

    Did you try this with a 15V supply? As long as connections are made exactly as they are shown in Figure 1, then there should be no concerns/issues. Have you tried to use a different XTR110? Perhaps doing a swap could give us some insight here.